An apparatus and method is known for sterilizing articles or items in an autoclave having steam as a medium and provided with an outer wall of a pressure vessel and an inner wall that is not a pressure vessel but defines a chamber to receive the articles to be sterilized. In this known apparatus, the chamber is surrounded by an outer space between said outer and inner walls. Furthermore, the autoclave has a steam supply conduit connected to the outer space and a connection between the latter space and the chamber. This known autoclave type does not operate satisfactorily since the operating procedure has to be carefully supervised and the results controlled. It is well known that the articles to be treated are not always rendered sterile after treatment and because of this uncertainty the treatment time is extended beyond what should theoretically be necessary to render said articles sterile. It has been found through investigation that the irregular treatment of the articles in the autoclave results since part of the steam supplied to the autoclave is condensed in the space between the chamber and the outer wall and that at least part of the condensate is entrained by the flow of steam being transferred from the space to the chamber. In some cases this flow will hold an amount of condensate greater than the amount formed only by the condensation of steam when the items or articles are heated from room temperature to the desired sterilization temperature. Moreover, it is well-known that the presence of water in or on the articles to be treated obstructs the killing of bacteria and involves a great risk of recontamination of the sterilized material or articles.
In addition to the disadvantage of uncertainty with respect to the result of the sterilization treatment, the above mentioned condensation of steam in the space and in connection with the chamber causes considerable heat losses and consequently extra costs for the sterilization treatment. Furthermore, there will be an additional cost due to prolonged treatment in order to achieve the desired result.
It is an object of the present invention to overcome the disadvantages of the prior construction and achieve both reliable treatment and lower cost for said treatment.
It is another object of the present invention to provide a sterilization treatment in which steam is supplied to an autoclave an an almost constant pressure difference is maintained between the outer space and the chamber, and this result is effective since the connection between the outer space and the chamber is a special design and a quantity of steam is discharged from the chamber. The aforesaid connection is so constructed as to cause a given pressure difference between the outer space and the chamber and further that the chamber has a restricted outlet.
It is an object of the present invention to provide an arrangement whereby the flow velocity of the steam between the outer space and the chamber is so chosen that there will be a minimum of energy losses.
It is another object of the present invention to provide an autoclave in which the risk is eliminated that a steam flow in the connection between the outer space and the chamber forms a constant source of transfer of condensate from said space to said chamber.